Protonation of polyaniline with lightly sulfonated polystyrene

Protonation of polyaniline base with lightly sulfonated polystyrene in polar solvents such its dimethyl sulfoxide and N-methyl-2-py~olidone was investigated by UV-Vis absorption spectra. As the molar ratio of sulfonated polystyrenelpolyaniline increases, the conversion from polyaniline base form to salt form is observed owing 10 incrensed protonation. The isosbestic point clearly shows that quinoid unit and semiquinoid unit are in equilibrium. They are functions of the sulfonic acid concentration and solvent medi ii.